The present invention relates to a method of remediating soil contaminated with hazardous substances. More particularly, the invention relates to a method of reducing the amount of carbon disulfide (CS.sub.2) in the soil through chemical oxidation.
In recent years, an increased awareness of preserving the environment has caused the Environmental Protection Agency (EPA) to take measures to counter the release or threat of release of hazardous substances from soil. The EPA investigated certain soils and determined that in some areas, there were hazardous concentrations of certain chemicals including CS.sub.2. The EPA has actually issued orders to remove CS.sub.2 contaminated soil.
CS.sub.2 can be converted to sulfate, a nonhazardous substance, by a chemical process known as alkaline oxidation. Alkaline oxidation of CS.sub.2 can be achieved with the use of a reagent containing a peroxide radical. However, oxidation of CS.sub.2 is a highly exothermic reaction which can release undesirable gaseous by-products such as H.sub.2 S. Furthermore, the addition of oxidant to CS.sub.2 can produce potentially explosive and flammable consequences.
Prior methods of remediating CS.sub.2 -contaminated soil included excavation of the contaminated soil. However, CS.sub.2 is highly volatile and can ignite or explode when exposed to air. Excavation of soil to remove CS.sub.2 creates the hazards associated with exposing CS.sub.2 to air. A process to remediate CS.sub.2 -contaminated soil without exposing CS.sub.2 to air is therefore desirable.
To date, there have been a number of methods developed to remediate contaminated soil. Examples include excavation and soil washing, electromigration, volatilization, incineration and land farming.
In addition, U.S. Pat. No. 5,868,523 describes an injection system to introduce biologicals, nutrients, water and air for bioremediation of contaminated soil and groundwater. The penetration can be both vertical and horizontal and does not disturb the soil in place. However, the '523 reference does not address rernediation of CS.sub.2 -contaminated soil or the unique difficulties and hazards associated with handling CS.sub.2.
U.S. Pat. No. 5,755,285 describes concentrating contaminants in one area of the soil and excavating the area. The technology disclosed in the '285 reference involves the use of bore holes made in the soil and injection of a medium to cause harmful substances to migrate and concentrate to a smaller soil area. Excavation work is thus reduced to a great extent. The '285 reference does not address remediation of CS.sub.2 -contaminated soil by treatment of the soil, nor does it address the difficulties and hazards encountered while treating CS.sub.2.
U.S. Pat. No. 5,536,898 describes immobilizing organic chemical waste in soil by absorption with biogenetic amorphous silica. The '898 reference discloses the mixing of untreated particulate rubber and biogenetic amorphous silica with soils contaminated with organic compounds in order to immobilize such compounds (i.e. they are no longer reactive) sufficiently to pass EPA requirements. The '898 patent does not address remediation of CS.sub.2 -contaminated soil by treatment of the soil, nor does it address the unique difficulties and hazards encountered while treating CS.sub.2.
Other disclosures related to degrading contaminants within the soil include U.S. Pat. No. 5,840,191, which describes microbial degradation of soil contaminants. Soil contaminated with one or more organic species and one or more metal species is first treated with microbial agents to break down the organic compounds followed by treating the same soil with microbially produced sulfuric acid to solubilize and leach the metal species as a metal sulfate, and finally bioprecipitating the metal sulfate.
Similarly, U.S. Pat No. 5,667,690 describes breaking down organic compounds (generally hydrocarbons) in solids, water or gas by using a complex of a transition metal and a polyamine in the presence of a peroxide. These complexes are injected into the medium by a pump.
None of the technologies mentioned hereinabove address remediation of CS.sub.2 -contaminated soil by treatment of the soil, nor do they address the unique difficulties and hazards encountered while treating CS.sub.2.
Thus, there is a need for a method to remediate CS.sub.2 -contaminated soil which avoids the potential hazards associated with CS.sub.2 oxidation.